Automotive, truck and other vehicular exhaust systems typically include conduit for directing exhaust gas from an engine to a remote location. Such exhaust systems often include a muffler, catalytic converter, resonator, or a combination thereof for treating the exhaust gas before it is discharged to the atmosphere. To accommodate various design criteria, exhaust gas systems usually include several exhaust conduits, tubes, hoses or pipes of various shapes and lengths that are connected together to form a fluid path for the exhaust gas.
The most common way of interconnecting consecutive conduits is to utilize a lap joint. To make a lap joint, one end of a first conduit is inserted within an end of a second conduit. The conduits are then clamped at the region where the conduits overlap. A typical clamp functions to crush, crimp, or otherwise deform the outer conduit against the inner conduit. The ends of the outer conduit typically include a plurality of longitudinal slots spaced about its circumference to facilitate crimping or otherwise deforming the outer conduit against the inner conduit.
U.S. Pat. No. 2,825,421 discloses a lap joint that uses "open ended" crimping slots. Typical "open ended" slots are generally u-shaped and extend longitudinally inward from a tube end for a distance of about 1.0 to 3.0 inches. A problem with "open ended" slots is that the slots can be difficult to seal and sometimes allow water to enter into an exhaust system. To address the problems associated with "open ended" slots, "captured" slots have been developed. "Captured" slots, such as those disclosed in U.S. Pat. Nos. 4,629,226, 4,270,689 and 4,113,289, do not extend completely to the end of an exhaust tube, and include two longitudinally spaced-apart closed ends.
While "captured" slots provide some advantages over "open ended" slots, "open ended" slots are still desirable for some situations. For example, "open ended" slots can be useful when a pipe is required to be unclamped and removed from another pipe, and then later reclamped with the same pipe. "Open ended" slots are desirable in this type of situation because, as compared to "captured" slots, "open ended" slots are easier to spread open after having been previously clamped at a lap joint. The need to unclamp and reclamp lap joints is common in the large truck industry. For example, new trucks are commonly "piggybacked" on one another during transport from the factory to dealers. To comply with freeway overpass clearance requirements, it is often necessary in these situations to remove the vertical tailpipes on the piggybacked trucks during transport, and reinstall the tailpipes at the dealer location. "Open ended" slots are advantageous because they facilitate the removal of tailpipes for transport to the dealers, and also facilitate the reinstallation of the tailpipes. Re-usable clamps are advantageous for the same reasons.
A variety of clamps have been developed for use in association with lap joints. One common clamp is known as a guillotine or saddle-type clamp. This clamp includes a u-bolt which is mounted on a saddle. The unbolt includes a concave portion that opposes a corresponding concave portion of the saddle. The saddle and u-bolt are forced toward each other through the use of a pair of nuts that are threaded on the legs of the un-bolt. U.S. Pat. Nos. 2,719,345 and 4,270,689 disclose guillotine or saddle-type clamps configured as described above.
Strap clamps have also been developed for use in sealing lap joints. Strap clamps can be divided into two categories including (1) wide band clamps; and (2) narrow band clamps. Wide band clamps are commonly formed of a band of relatively thin, ductile metal having a width frequently greater than three inches. When used to seal a lap joint, a typical wide band clamp is stressed beyond its elastic limit to conform intimately with the outer surfaces of the pipes forming the lap joint. U.S. Pat. No. 3,944,265 discloses a wide band clamp as described above.
Narrow band clamps are frequently used to seal lap joints having "captured" slots and are commonly made from bands of metal having widths equal to or less than 1.5 inches. Narrow band clamps are typically substantially thicker than their wide band counterparts. This increased thickness is useful in providing sufficient clamping force to adequately crush "captured" slots. Due to the thickness of material used in narrow band clamps, narrow band clamps usually are not stressed beyond their elastic limit when used to seal a lap joint. Consequently, narrow band clamps are more readily reusable than wide band clamps.